Electron discharge tube



C. F. MILLER ELECTRON DISCHARGE TUBE July 14, 1942.

Original Filed. Feb. 8, 1938 3 Sheets-Sheet 1 W Km July 1942- c. F.MILLER ,289,

ELECTRON DI S CHARGE TUBE Original Filed Feb. 8, 1958 3 Sheets-Sheet 2A-TTOK/VEY July 14, 1942. c. F. MILLER 2,289,588

M ELECTRON DISCHARGE TUBE 7 Original Filed Feb. 8, 1958 3 Sheets-Sheet 5d is warm A 771 EN!) Patented July 14, 1942 l I ELECTRON DISCHARGE TUBECarl F. Miller, Corning, N. Y., assignor to Hygrade SylvaniaCorporation, Emporium, Pa., a corporation of Massachusetts Originalapplication February 8, 1938, Serial No. 189,295. Divided and thisapplication May 9, 1941, Serial No. 392,605

11 Claims. 250-275) This invention relates to electron discharge tubesand more especially to tubes of the electrostatically shielded type.

A principal object of the invention is to provide a tube of the glassenvelope type having a minimum inherent input capacitance and a minimuminherent output capacitance.

It has been known for many years that in order to utilize the gain of agrid controlled electron discharge repeater tube to full advantage athigh frequencies, it is necessary to shield the input electrodes fromthe output electrodes electrostatically. One example of such tube whichhas achieved wide utility in this respect, is the socalled screen-gridor shield-grid tube. While this type of tube has been found satisfactoryfor certain purposes, it represents a compromise with total electricshielding with the result that at ultra-high frequencies the tubespossible gain is not fully achieved. This compromise has beennecessitated heretofore, by the difficulty of shielding the electrodesof the mount when arranged in the conventional manner, this conventionalarrangement limiting the manner in which electrostatic shielding can beapplied. As a matter of fact, in the well-known shield-grid type oftube, because of the limitations of the shielding system, it has beennecessary to remove the control-grid lead to the greatest possibledistance from the plate lead, thus involving the use of a cap-contactwhich is located at the top of the glass bulb. Apart from the difficultyand expense of applying and fastening this special top cap, is theadditional disadvantage that a separate flexible lead must be employedto make contactwith the cap in order to connect the control grid incircuit. In other words, a radio tube of the conventional shield grid,top-contact type, cannot be completely connected in circuit merely byplugging the tube into its socket, but a separate operation of applyingthe flexible contact to the control grid cap-contact is necessary. Theseflexible leads and top-caps have been the source of many annoyingdisturbances in the operation of the usual broadcast radio receiver andare especially disadvantageous in ultra-high frequency applications.

Accordingly, it is another principal object of this invention to providea tube of the glass envelope type having a substantially totallyelectrostatically shielded mount, and with all the contact membersdisposed at one end of the tube.

Another object is to provide a radio tube having a series of contactprongs at its lower end together with improved shielding arrangements toshield electrostatically the major part of the prongs including the partactually intended to engage in the cooperating contact socket.

A further feature relates to a novel form of shield for the lead-inconductors or prongs of a radio tube.

A further feature relates to a tube of the type wherein the contactprongs are directly sealed through the glass header of the tube inconjunction with a special form of coupling member mounted interiorly ofthe tube adjacent the said header for connecting the various electrodesto the respective prongs.

A still further feature relates to the novel organization, arrangementand relative location of parts which constitute an improved tube forultra-high frequency work.

Other features and advantages not specifically enumerated will beapparent after a consideration of the following detailed descriptionsand the appended claims.

While the invention is capable of application to any type of radio tubehaving two or more electrodes in the mount or electrode assembly, it isparticularly advantageous in tubes wherein the control grid or signalinput electrode is to be totally shielded electrostatically from ananode or output electrode. While therefore, the invention will bedisclosed herein as embodied in a radio tube of the pentode type, thisis done merely for purposes of explanation and it will be obvious thatvarious novel features can be applied to tubes having a greater or lessnumber of electrodes. Accordingly, in the drawings:

Fig. 1 is a vertical sectional view of a tube of the pentode typeembodying the invention.

Fig. 2 is a horizontal sectional view of Fig. 1 taken along the line 2-2thereof.

Fig. 3 is a horizontal sectional view of Fig. l taken along the line 3-3thereof.

Fig. 4 is a bottom view of Fig. 1.

Fig. 5 is a modification of Fig. 1.

Fig. 6 is a horizontal cross-sectional viewof Fig. 5 taken along theline 66 thereof.

Fig. '7 is an enlarged perspective view of the prong shield.

Fig. 8 is an exploded view of part of Fig. 5.

Figs. 9 to 12 are views of a preferred embodiment of the invention.

stantially fiat bottom 2 and a rim 3. Preferably the bottom 2 is of muchthicker glass than the wall I of the bulb, and the glass rim 3preferably tapers in thickness from the bottom 2 to the wall I where itis sealed. The cup 2 and its rim 3 are preferably formed as a unitseparate from the bulb I, to which it is later sealed after theelectrode assembly or mount has been assembled as described hereinbelow.Preferably the bottom 2 is formed with a series of integral bosses d inthe regions where the rigid metal rods 5 to l2 inclusive, are sealedtherethrough, and these rods are sealed into member 2 in a vacuum-tightmanner as described in detail either in U. S. Patent No. 2,219,574, orin U. S. Patent No. 2,250,183.

As shown, the rods 5 to I2 extend upwardly into the envelope to act assupport or current lead-in members for the various electrodes of themount; these rods also extend downwardly to act as rigid contact prongswhereby the tube when completely finished can be plugged into a suitablecontact socket having in series of spring contacts to receiverespectively prongs 5 to E2. Preferably, although not necessarily, thebottom 2 is of 705-AJ glass, and the rods 5 to [2 are of a special alloywhich is capable of being directly sealed to the glass 2 in avacuum-tight manner. As examples of such alloys may be mentioned, Kovaran alloy consisting substantially of Fe, Ni, Co; or Fernico an alloyconsisting substantially of Fe, Ni, Co. Preferably the lower ends ofprongs 5 to l2 inclusive are provided with rounded points to facilitateinsertion of the tube into a socket.

As shown more clearly in Fig. 2, the contact prongs are arranged in acircle around the center of member 2, and the latter is provided with acentral opening 13 which is in communication with the tipped-off exhausttubulation It. Supported on the inwardly projecting ends of rods I1 andI8, is any well-known form of radio tube mount or electrode assembly.Preferably this assembly is of the unitary type, that is with theelectrodes assembled as a unit between upper and lower mica discs l5 andit. An example of a typical unitary mount is found in U. S. Patent No.2,084,734. The main metal uprights l1, 83, pass through a shallow metalcup l9 and are welded at their lower ends to the prongs 5 and 9respectively. Cup [9 is held in place on uprights H and I8 by means ofdownwardly projecting struck-out metal tabs which are welded to saiduprights. The bottom of member 59 is provided with a longitudinal slot20 to allow the side rods of the various electrodes as well as thecathode, to extend downwardly without being short-circuited by memberl9. The ends of slot 20 are struck-up to form tabs 2| to support thelower mica disc IE which is fitted within the rim of cup is. Mica I6 isheld in place in any suitable manner, for example by swaging theuprights I! and I8 or by means of metal lugs or tabs Welded to saiduprights and bearing against the upper face of disc it. In the wellknownmanner disc I6 is provided with a series of perforations to receive thelower ends of the various electrode side rods and the cathode.

The drawings show an electrode assembly of the pentode type comprising acentral electronemitting cathode sleeve 22 having an insulated heaterfilament 23 on its interior, the ends of which are connectedrespectively to prongs 1 and B. The electrode assembly also includes acontrol grid in the form of a fine wire helically wound around the siderods 24, 25, the side rod 25 being connected at its lower end to prongH1; a shield grid similar to the control grid and wound around the siderods 23, 2? with side rod 28 connected at its lower end to prong 52; asuppressor-grid likewise in the form of a fine wire helically woundaround side rods 28, 29; and a tubular metal plate welded to side rods3|, 32. Side rod 3! extends downwardly through an enlarged opening (notshown) in member !9 so as not to be short-circuited therewith, and iswelded to prong 6. The lower end of side rod 32 passes through mica IEbut does not reach member [9. The upper ends of plate side rods 35, 32are provided with tabs (not shown) to support the top mica H which issimilar to mica l6 and is provided with a similar series of side rod andcathode perforations.

It will be noted that the suppressor-grid side rods 28, 29, extendupwardly further than the remaining side rods, and welded to the siderods 28, 29 is a flattened tubular metal strip 3. which bears againstthe upper face of mica l to hold it in place. A short metal tab 35connects the cathode sleeve 22 to member 3t, consequently thesuppressor-grid and the cathode are at the same shielding potential.

For the purpose of shielding the electrodes and the contact prongseleotrostatically and for preventing undesirable radiation from theelectrode system, there is provided an inverted metal cup 36 having atop metal closure 3! with a longitudinal slot 38 in registry with member34. The ends of slot 38 are provided with struck-up lugs 39 which arewelded to the suppressor-grid side rods 28, 29. The shield 36 extendsdownwardly beyond, but in close fitting engagement with, the rim ofmember iii to which it is welded at a plurality of points around itsperiphery. It should also be noted that member 3%: extends downwardly asuiiicient distance to overlap the prongs 5 to i2 inclusive, and tooverlap the rim to of a metal cup member within which the tube isseated. This metal cup member is preferably of the constructiondisclosed in detail in U. S. Patent No. 2,238,025, and comprises aspider-like base 35 having a series of circular openings to receive theglass bosses 3 and the several contact prongs. The base is held in placeon the tube in any well-known manner as for example by a ring of cement42.

Preferably, the member 4| carries centrally thereof a hollow tubularmetal member 45 which performs the double purpose of a protectivehousing for the glass tubulation i4, and a supplemental electrostaticshield between the various contact prongs. Member 45 may be formed witha longitudinal guiding rib or key 46 to facilitate insertion of the tubeinto its socket and member Q5 may also be formed with a circumferentiallocking groove ii adapted to engage a suitable grounded contact spring58 in the contact socket (not shown). Preferably the prong 9 which isconnected to members 19, 36 and to the suppressor-grid, and cathode isconnected by a strap @9- to the member 4|. In order to complete theelectrostatic shielding of the contact prongs, there is provided a metaldisc 59 (Fig. 7) having a central opening 5| in registry with thetubulation opening l3. Member 55 also has a vertical metal extension 52adapted to enclose the plate prong 5 as shown more clearly in Figs. 1, 2andv 4. Extension 52 is provided with wings 53, 5-3, which areinterposed between the plate prong 6 and the adjacent prongs 5 and l.Member 52 is electrically connected to the mount shield by means ofmetal tabs 55' welded to member I9 and member 52.

By the foregoing constuction, the entire mount as well as the contactprongs are substantially completely electrically shielded. The mount issubstantially entirely enclosed within the members I9, 36 and 31 and thecontact prongs are shielded by the member 36, which overlaps the member40, and by the members 4|, 50 and 52 as well as by the member 45. Thearrangement disclosed reduces to the smallest practical extent theseparation between the lower end of the mount and the exposed ends ofthe various contact prongs and even the portion of the contact prongsbetween the base of the bulb and the mount are substantially entirelyshielded. Consequently, the tube is very well adapted to use in highfrequency work and with the structure disclosed, interelectrodecapacitances lower than 0.004 mmfd. have been obtained. Thus it ispossible to construct a tube of the shield grid, pentode or similar typewith all the connections at the lower end of the tube and avoiding theusual flexible lead for connecting the control grid in circuit. Ifdesired, the bulb portion of the envelope may be provided with aperipheral bead 56. While Fig. 1 shows a shield for the plate prong, itwill be obvious that a plurality of shields similar to member 52 may becarried by disc 50 each shield enclosing an appropriate one of theprongs.

Instead of shielding the plate prong, the grid prong may be shielded.Such an arrangement is disclosed in Figs. 5, 6 and 8. In this embodimentthe tube envelope, mount and base and other parts are similar to thecorresponding parts of Fig. 1 and these corresponding parts bear thesame designation numerals. However, this embodiment differs from that ofFig. 1 in the manner of making connection to the filament wires and inthe manner of shielding the grid prong. In view of the proximity of thelower end of the mount to the upper ends of the contact prongs, it issometimes difficult to weld the free ends or terminals of the filamentor heater to the corresponding prongs. This difficulty is overcome inthe embodiment of Figs. 5, 6 and 8 by providing a mica bridge 60 asshown in detail in Fig. 8. Member 60 is provided with perforations 61,62, whereby it can be assembled over the prongs 5 and 9 as shown in Fig.6, prior to assembly of the mount in place. Before assembling the bridgein place, the shield disc 50 is positioned against the upper face ofmember 2 and with the pin shield extension 52 and wings 53, 54 enclosingthe control grid prong I0. The disc also carries two metal strips ortabs 63, 64, which are welded at their end 65, 66 to the lower end ofshield member 36. After assembling the mount in place, members 63 and 64therefore serve as supporting means for the mount in addition toeffecting an electrical connection between the various parts of thecomposite shielding system. The mica bridge 6|] is provided with a notch67 to accommodate the arm 63 and also with a shoulder 68 to accommodatethe arm 64. In order to carry the shielding of the grid leadin to themaximum possible extent, the wings 53 and 54 (Fig. 8) instead ofextending vertically straight as in Fig. 7, are provided with aninclined or trough-like portion 11 which extends upwardly intoengagement with the metal cup I9 to which it may be welded by suitabletabs similar to the tabs 55 of Fig. 1. The trough-like portion 11 of theshield encloses-the metal strap 18 which connects the lower end ofcontrol grid siderod 25 to its contact prong I0. With this arrangementthe control grid and its entire leadin connection are completelyshielded electrostatically from the plate lead both interiorly andexteriorly of the tube, the external shielding being effected by members40, 4| and 45.

The central portion of bridge 60 is provided on opposite edges withpairs of notches 69, 10; II, 12, to receive the T-shaped metal strapmembers 13, I4, to which the ends of the filament are welded. Thefilament prongs I and 8 are connected by wires I5, 16 to members 13, 14.The connection of the remaining electrodes to their respective contactprongs is the same as already described in connection with Fig. 1. Inthe embodiment of Fig. 5, the provision of the mica bridge with thestraps I3, 14, enable the filament prongs I and 8 to be electricallyconnected to members I3 and I4 prior to assembly of the mount in place,and the final welding of the filament ends to the upwardly projectingmembers 13, 74, can be effected readilyand effectively. Where thefilament ends are welded directly tothe prongs I and 8' as in Fig. 1 forexample, the alloy of the prongs and their mass may render it verydifficult to secure a satisfactory weld. Furthermore, the heat of suchdirect welding may result in undesirable strains being set up in theregions of member I where the prongs are sealed in. These disadvantagesare overcome with the structure of Figs. 5 to 8.

Referring to Figs. 9 to 12, there is shown a preferred modificationwhich combines certain of the structural advantages of the precedingembodiments. The parts of Figs. 9 to 12 which are identical with thoseof the preceding embodiments are designated by the same numerals. Thusthe glass enclosing envelope comprises a tubular portion I which issealed to a cup-shaped glass base 2 having a rim 3 of tapered thickness.Base 2 is provided with a circularly arranged series of bosses 4 throughwhich the rigid metal rods or contact prongs 5 to I2 are directly sealedin a vacuum-tight manner.

The electrode assembly or mount includes the central indirectly heatedcathode 22 which is coated with e1ectron-emitting material as indicated,the cathode being connected by wire 22a to prong 9. The filamentinsulatingly supported inside the cathode sleeve has its terminalsconnected to prongs I and 8 by a special connecting arrangement to bedescribed. The first or control grid is Wound around side rods 24 and25, side rod 24 being connected by wire 24a to prong Ill. The second orshield grid is wound around side rods 26 and 21, side rod 2'! beingconnected by wire 21a to prong l2. The third or suppressor grid is woundaround the side rods 28 and 29, rod 29 being connected by wire 29a toprong I I. The plate 30 is directly connected to prong 6.

The electrodes are assembled between the upper and lower mica spacerdiscs I5, I6, preferably to form a unitary assembly. For this purpose,the upper and lower edges of plate 30 may be provided with integralshouldered spacer tabs 3041 which have their ends bent back against themica discs, as disclosed for example in U. S. Patent No. 2,118,765.

The entire electrode assembly is enclosed with- V ing the evacuation ofthe tube.

annular flange 36c is welded to the cap and rests against the top micaHi. If desired, a getter cup or carrier 3611 may be supported centrallyabove the mount by a doubly bent wire 36c welded to cap 36b and to thegetter cup as shown.

Shield 36a is completed adjacent its lower end by the cup-shaped metalmember H] which has its rim welded to the shield. For this latterpurpose, the shield is provided with two small diametrically oppositeslots 36 to allow. a suitable welding tool to be inserted. If desired,the slots 36] may be closed by a metal flap or cover (not shown) afterthe welding is effected. Cup I9 is provided with alongitudinal slot 20to allow the various side rods and the cathode to project downwardlywithout being short-circuited, and mica disc l preferably rests on theup-turned ends 2| of this slot.

As described in connection with Fig. l, shield 36a extends downwardly sothat it overlaps the metal rim of the cup-shaped metal base which has aspider-like bottom 4| as shown more clearly in Fig. 4. Preferably, thecontact prong 5 iselectrically connected to base 4| as described inconnection with Fig. 4. Preferably also, shield 35a does not extend downso far that it interferes with the welding of the various wires to theprongs.

The electrostatic shielding of the mount is completed by a metal discmember 80 (Fig. 12) having a pair of vertical channeled extensions 8|,82, each extension being provided with a pair of tabs 83 which arewelded to the metal cup IS. The disc 88 is provided with a centralopening 84 so as not to obstruct the exhaust tubulation |4 dur- Themember 8| is disposed so that it encloses the plate prong 6 and themember 82 is disposed so that it shields the cathode prong 9 from thegrid prong I0.

Each of the members 8| and 82 are provided with a vertical slit toreceive a mica bridge member 85 having a pair of openings 86. Strappedaround an edge of each of the openings 86 is a metal strap 81 having alug 88 and a flexible connecting tab 89. The lugs 88 are connected tothe ends of the heater filament as shown more clearly in Fig. 9, and thetabs 89 are welded or otherwise connected to the prongs l and 8 as shownmore clearly in Fig. 11. Preferably, as described above, the base member4| has electrically fastened thereto a downwardly depending hollow metalboss or keying member 45 having a vertical key 46. The member 45 isadapted to be grounded or connected to a suitable source of basepotential when the tube is inserted in a corresponding contact socket,it being understood that the base 48 is fastened to the tube in anywell-known manner for example by a ring of basing cement 42.

While specific embodiments of the invention have been illustrated, itwill be understood that various changes and modifications may be madetherein without departing from the spirit and scope of the invention.

This application is a division of application Serial No. 189,295, filedFebruary 8, 1938, now Patent No. 2,250,184.

What I claim is:

1. An electron discharge device comprising an enclosing vessel having astem, an electrode assembly comprising. a plurality of elements axiallymounted within said vessel, a plurality of leadin conductors, in saidstem parallel to the axis thereof and mounted in arcuate form, and acoupling element preformed and assembled as a unit independent of saidelectrode assembly including an insulating member extending transverselyto said axis between said stem and said assembly and carrying aplurality of metal projections for completing the electrical connectionsbetween certain of said lead-in conductors and at least one of saidelements.

2. An electron discharge device comprising an enclosing vessel having astem, an electrode assembly axially mounted within said vessel, aplurality of lead-in conductors sealed in said stem parallel to the axisthereof and arranged in arcuate form, and a coupling element preformedand assembled as a unit independent of said electrode assemblytransversely positioned between said assembly and said stem, saidelement comprising an insulator having a plurality of metal projectionswith their ends connected to at least one of said elements and theiropposite ends connected to a pair of lead-in conductors, saidprojections being anchored to said insulator so that bending of aprojection at one end will not distort the opposite end attached to saidelement.

3. An electron discharge device comprising an electrode assembly havinga plurality of electrodes including a heatable filament, an insulatedspacer at each end of said electrode for coupling them together, a stemhaving spaced conductors sealed therein parallel to the axis thereof, acap portion enclosing said assembly and sealed to said stem, and aninsulating coupling element extending at right angles with respect tosaid electrodes and said conductors carrying individual metalprojections secured thereto and attached to said filament and to certainof said conductors, said coupling element with it metal projectionsbeing preformed and assembled as a unit independent of said electrodeassembly.

4. An ultra-high frequency multi-electrode device comprising a moldeddish-like stem having short lead-in conductors mounted in a circularboundary and parallel to the axis of said stem, an electrode unit ofdifferent diameter than the boundary radius of said lead-in conductorsmounted in said stem, an enclosing cap surrounding said unit and sealedto the periphery of said stem, and a coupling element preformed andassembled as a unit independent of said electrode unit interposedtransversely between said unit and said conductors having wire-likemembers connected between said electrode unit and said conductors.

5. An electron discharge device comprising an electrode assembly havinga plurality of electrodes including a heatable filament, a dish-likeglass stem having a plurality of lead-in conductors sealed directlytherethrough and arranged around and parallel to the axis of the stem, abridge of insulation extendin transversely across the stem between theassembly and stem, 3, pair of metal strips anchored to said bridge saidbridge and its metal strips being preformed and assembled as a unitseparate from said electrode assembly, said strips each having an endwelded to an end of said filament and another end welded to one of saidlead-in conductors.

6. An electron discharge device according to claim 5 in which saidbridge is of mica and said strips are interlocked therewith.

7. An electron discharge device according to claim 5 in which the bridgeis in the form of a mica strip mounted with its plane substantiallyparallel to the bottom of said stem.

8. An electron discharge device according to claim 5 in which thebridige is in the form of a mica strip mounted with its planesubstantially perpendicular to the bottom of said stem.

9. An electron discharge device according to claim 5 in which saidlead-in conductors are of rigid metal alloy which is difiicult to welddirectly to the ends of the filament.

10. An electron discharge device according to claim 5 in which theinsulation bridge is interlocked with a metal shield having a portion atleast partially enclosing one of said lead-in conductors.

11. An electron discharge device according to claim 5 in which saidinsulator bridge is interlocked with a metal shield member having aportion lying substantially parallel to the bottom of said stem and achanneled portion at least partially enclosing one of said lead-inconductors.

CARL F. MILLER.

